Sea levels rose faster than thought since 1900; Future projections may need to be recalibrated

 

Credit: Photo by Robert Kopp

Correcting estimates of sea level rise

Posted: 14 Jan 2015 11:05 AM PST

The acceleration in global sea level from the 20th century to the last two decades has been significantly larger than scientists previously thought, according to a new study. Previous estimates of global sea-level rise from 1900-1990 had been over-estimated by as much as 30 percent, researchers suggest. “What this paper shows is that sea-level acceleration over the past century has been greater than had been estimated by others,” said Eric Morrow, a recent Ph.D. graduate. “It’s a larger problem than we initially thought.” The acceleration in global sea level from the 20th century to the last two decades has been significantly larger than scientists previously thought, according to a new Harvard study. The study, co-authored by Carling Hay, a post-doctoral fellow in the Department of Earth and Planetary Sciences (EPS), and Eric Morrow, a recent PhD graduate of EPS, shows that previous estimates of global sea-level rise from 1900-1990 had been over-estimated by as much as 30 percent. The report, however, confirms previous estimates of sea-level change since 1990, suggesting that the rate of sea-level change is increasing more quickly than previously believed. The new work is described in a January 14 paper published in Nature. ….Previous estimates had placed sea-level rise at between 1.5 and 1.8 millimeters annually over the 20th century. Hay and Morrow, however, suggest that from 1901 until 1990, the figure was closer to 1.2 millimeters per year. But everyone agrees that global sea level has risen by about 3 millimeters annually since that time, and so the new study points to a larger acceleration in global sea level. “Another concern with this is that many efforts to project sea-level change into the future use estimates of sea level over the time period from 1900 to 1990,” Morrow said. “If we’ve been over-estimating the sea-level change during that period, it means that these models are not calibrated appropriately, and that calls into question the accuracy of projections out to the end of the 21st century.“….

 

Carling C. Hay, Eric Morrow, Robert E. Kopp & Jerry X. Mitrovica. Probabilistic reanalysis of twentieth-century sea-level rise. Nature, January 2015 DOI: 10.1038/nature14093

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